[S]tandard-issue hog farming involves the practice of tail docking—that is, shortly after piglets are born, their tails are cut off short. You might ask: why would we need to cut the tails off of pigs? Good question! Pig tails need to be cut off, in factory farms, because the pigs stand around all day in tiny, crowded spaces. Some of them seek to amuse themselves by biting other pigs on the tail. Often, the pigs being bitten are really just too listless to stop the biting. So their tails bleed. This can lead to infection, of course, but it could also lead to cannibalistic attacks on the bleeding hog—after all, pigs are omnivores! Now, having the tails docked won’t prevent tail biting, because there’s still a stump. But the stump is extremely sensitive, so even an otherwise very listless pig is likely to quickly put a stop to anyone’s gnawing on his stump. Hence, the infections or cannibalistic attacks can be prevented.
Now, tail docking is an extra task, requiring extra labor from pig farmers. So it would be nice if it were unnecessary. Fortunately, science plans to come to the rescue here—we’re working on isolating the stress gene in hogs, so that we can create new hogs that can be crowded into horrific conditions without becoming stressed out. If they’re not stressed into listlessness, they’re more likely to react quickly to anyone’s biting their tail. Problem solved.